1. Field of the Invention
The present invention relates to a projection image display apparatus for making a user recognize a full-color image by synchronizing image display and light emission.
2. Related Background Art
Various conventional image display apparatuses for displaying images include apparatuses using CRTs, liquid crystal panels, and the like. Some apparatuses designed to display color images use sequential color schemes (field sequential scheme and color sequential switching scheme). The structure of an image display apparatus using such a scheme will be described below with reference to FIG. 14.
Referring to FIG. 14, an image display apparatus 100 of this type includes an image display element P for sequentially displaying gradation images and an illumination device BL2 for sequentially irradiating the image display element P with light beams of different colors. This apparatus is configured to make a user recognize each gradation image as a color image by synchronizing image display and light emission and make the user recognize a full-color image by color-mixing a plurality of color images.
The illumination device BL2 has a lamp 2 for emitting white light toward the image display element P and a color filter plate 3 which is placed between the image display element P and the lamp 2 and driven to rotate. The color filter plate 3 is divided into filter sections 3R, 3G, and 3B of three colors, i.e., red, green, and blue. When the color filter plate 3 is driven to rotate, white light is sequentially split into light beams of the respective colors, and the image display element P is sequentially irradiated with the respective color light beams. Note that as the lamp 2, a discharge lamp such as a metal halide lamp or mercury lamp having the characteristic shown in FIG. 6 (i.e., a continuous intensity distribution characteristic in the visible wavelength region of 400 nm to 700 nm) is used.
In such an apparatus, it is difficult to improve both the color reproducibility and luminance of a color image to be displayed. As the color reproducibility is improved, the image luminance decreases, and vice versa. The quality (i.e., color reproducibility and luminance) of a color image is uniquely determined by the arrangement of a color filter plate (the number of transmission light wavelength regions or segments). In one image display apparatus, all images are displayed with the same image quality, and the image quality cannot be changed according to user""s taste.
Assume that
a transmission light wavelength region xcex94r2 of the red filter section 3R (light transmitted through this filter section has a wavelength region of a certain width, which will be referred to as a wavelength region) is about 600 nm or more as shown in FIG. 3,
a transmission light wavelength region xcex94g1 of the green filter section 3G is about 505 nm to 570 nm as shown in FIG. 3, and
a transmission light wavelength region xcex94b1 of the blue filter section 3B is about 505 nm or less as shown in FIG. 3.
In this case, the color purities of light beams improve, and the color reproducibility of a full-color image improves. However, since narrow wavelength regions are used, the image luminance decreases. In contrast to this, if each wavelength region is broadened (for example, the transmission light wavelength region xcex94r2 of the red filter section 3R is broadened to a region xcex94r1) or the number of segments of the filter plate is increased to set segments of four colors, i.e., red, green, blue, and white (U.S. Pat. No. 5,233,385), the image luminance can be increased, but the color purity of each color light beam deteriorates, resulting in a deterioration in color reproducibility.
Other background arts are disclosed in Patent Registration No. 2726417 and Japanese Laid-Open Patent Application Nos. 7-222185, 5-56440, and 4-6502.
It is an object of the present invention to provide an image display apparatus which can adjust image quality in accordance with the image to be displayed.
In order to achieve the above object, there is provided a projection image display apparatus which comprises an image display element for sequentially displaying gradation images, and an illumination device for sequentially irradiating the image display element with light beams of different colors, and allows a full-color image to be recognized by synchronizing display of the images and light emission,
wherein the illumination device includes a white light source for emitting white light toward the image display element, first filter means rotatably supported between the image display element and the white light source, first filter driving means for driving to rotate the first filter means, second filter means supported movably along the first filter means, and second filter driving means for driving or non-driving the second filter means in accordance with an image to be displayed,
the first filter means is divided into at least first to third filter sections with different transmission light wavelength regions, and driven to rotate by the first filter driving means to sequentially insert the filter sections in an optical path of the white light, and
the second filter means is driven by the second filter driving means such that, when the first filter section is inserted in the optical path of the white light, the second filter means is also inserted in the optical path, and, when the first filter section is removed from the optical path of the white light, the second filter means is also removed from the optical path.